GNU Readline Library

This document describes the GNU Readline Library, a utility which aids
in the consistency of user interface across discrete programs which
provide a command line interface.
The Readline home page is http://www.gnu.org/software/readline/.

1.1 Introduction to Line Editing

The following paragraphs describe the notation used to represent
keystrokes.

The text C-k is read as `Control-K' and describes the character
produced when the k key is pressed while the Control key
is depressed.

The text M-k is read as `Meta-K' and describes the character
produced when the Meta key (if you have one) is depressed, and the k
key is pressed.
The Meta key is labeled ALT on many keyboards.
On keyboards with two keys labeled ALT (usually to either side of
the space bar), the ALT on the left side is generally set to
work as a Meta key.
The ALT key on the right may also be configured to work as a
Meta key or may be configured as some other modifier, such as a
Compose key for typing accented characters.

If you do not have a Meta or ALT key, or another key working as
a Meta key, the identical keystroke can be generated by typing ESCfirst, and then typing k.
Either process is known as metafying the k key.

The text M-C-k is read as `Meta-Control-k' and describes the
character produced by metafyingC-k.

In addition, several keys have their own names. Specifically,
DEL, ESC, LFD, SPC, RET, and TAB all
stand for themselves when seen in this text, or in an init file
(see section 1.3 Readline Init File).
If your keyboard lacks a LFD key, typing C-j will
produce the desired character.
The RET key may be labeled Return or Enter on
some keyboards.

1.2 Readline Interaction

Often during an interactive session you type in a long line of text,
only to notice that the first word on the line is misspelled. The
Readline library gives you a set of commands for manipulating the text
as you type it in, allowing you to just fix your typo, and not forcing
you to retype the majority of the line. Using these editing commands,
you move the cursor to the place that needs correction, and delete or
insert the text of the corrections. Then, when you are satisfied with
the line, you simply press RET. You do not have to be at the
end of the line to press RET; the entire line is accepted
regardless of the location of the cursor within the line.

1.2.1 Readline Bare Essentials

In order to enter characters into the line, simply type them. The typed
character appears where the cursor was, and then the cursor moves one
space to the right. If you mistype a character, you can use your
erase character to back up and delete the mistyped character.

Sometimes you may mistype a character, and
not notice the error until you have typed several other characters. In
that case, you can type C-b to move the cursor to the left, and then
correct your mistake. Afterwards, you can move the cursor to the right
with C-f.

When you add text in the middle of a line, you will notice that characters
to the right of the cursor are `pushed over' to make room for the text
that you have inserted. Likewise, when you delete text behind the cursor,
characters to the right of the cursor are `pulled back' to fill in the
blank space created by the removal of the text. A list of the bare
essentials for editing the text of an input line follows.

C-b

Move back one character.

C-f

Move forward one character.

DEL or Backspace

Delete the character to the left of the cursor.

C-d

Delete the character underneath the cursor.

Printing characters

Insert the character into the line at the cursor.

C-_ or C-x C-u

Undo the last editing command. You can undo all the way back to an
empty line.

(Depending on your configuration, the Backspace key be set to
delete the character to the left of the cursor and the DEL key set
to delete the character underneath the cursor, like C-d, rather
than the character to the left of the cursor.)

1.2.2 Readline Movement Commands

The above table describes the most basic keystrokes that you need
in order to do editing of the input line. For your convenience, many
other commands have been added in addition to C-b, C-f,
C-d, and DEL. Here are some commands for moving more rapidly
about the line.

C-a

Move to the start of the line.

C-e

Move to the end of the line.

M-f

Move forward a word, where a word is composed of letters and digits.

M-b

Move backward a word.

C-l

Clear the screen, reprinting the current line at the top.

Notice how C-f moves forward a character, while M-f moves
forward a word. It is a loose convention that control keystrokes
operate on characters while meta keystrokes operate on words.

1.2.3 Readline Killing Commands

Killing text means to delete the text from the line, but to save
it away for later use, usually by yanking (re-inserting)
it back into the line.
(`Cut' and `paste' are more recent jargon for `kill' and `yank'.)

If the description for a command says that it `kills' text, then you can
be sure that you can get the text back in a different (or the same)
place later.

When you use a kill command, the text is saved in a kill-ring.
Any number of consecutive kills save all of the killed text together, so
that when you yank it back, you get it all. The kill
ring is not line specific; the text that you killed on a previously
typed line is available to be yanked back later, when you are typing
another line.

Here is the list of commands for killing text.

C-k

Kill the text from the current cursor position to the end of the line.

M-d

Kill from the cursor to the end of the current word, or, if between
words, to the end of the next word.
Word boundaries are the same as those used by M-f.

M-DEL

Kill from the cursor the start of the current word, or, if between
words, to the start of the previous word.
Word boundaries are the same as those used by M-b.

C-w

Kill from the cursor to the previous whitespace. This is different than
M-DEL because the word boundaries differ.

Here is how to yank the text back into the line. Yanking
means to copy the most-recently-killed text from the kill buffer.

C-y

Yank the most recently killed text back into the buffer at the cursor.

M-y

Rotate the kill-ring, and yank the new top. You can only do this if
the prior command is C-y or M-y.

1.2.4 Readline Arguments

You can pass numeric arguments to Readline commands. Sometimes the
argument acts as a repeat count, other times it is the sign of the
argument that is significant. If you pass a negative argument to a
command which normally acts in a forward direction, that command will
act in a backward direction. For example, to kill text back to the
start of the line, you might type `M-- C-k'.

The general way to pass numeric arguments to a command is to type meta
digits before the command. If the first `digit' typed is a minus
sign (`-'), then the sign of the argument will be negative. Once
you have typed one meta digit to get the argument started, you can type
the remainder of the digits, and then the command. For example, to give
the C-d command an argument of 10, you could type `M-1 0 C-d',
which will delete the next ten characters on the input line.

1.2.5 Searching for Commands in the History

Readline provides commands for searching through the command history
for lines containing a specified string.
There are two search modes: incremental and non-incremental.

Incremental searches begin before the user has finished typing the
search string.
As each character of the search string is typed, Readline displays
the next entry from the history matching the string typed so far.
An incremental search requires only as many characters as needed to
find the desired history entry.
To search backward in the history for a particular string, type
C-r. Typing C-s searches forward through the history.
The characters present in the value of the isearch-terminators variable
are used to terminate an incremental search.
If that variable has not been assigned a value, the ESC and
C-J characters will terminate an incremental search.
C-g will abort an incremental search and restore the original line.
When the search is terminated, the history entry containing the
search string becomes the current line.

To find other matching entries in the history list, type C-r or
C-s as appropriate.
This will search backward or forward in the history for the next
entry matching the search string typed so far.
Any other key sequence bound to a Readline command will terminate
the search and execute that command.
For instance, a RET will terminate the search and accept
the line, thereby executing the command from the history list.
A movement command will terminate the search, make the last line found
the current line, and begin editing.

Readline remembers the last incremental search string. If two
C-rs are typed without any intervening characters defining a new
search string, any remembered search string is used.

Non-incremental searches read the entire search string before starting
to search for matching history lines. The search string may be
typed by the user or be part of the contents of the current line.

1.3 Readline Init File

Although the Readline library comes with a set of Emacs-like
keybindings installed by default, it is possible to use a different set
of keybindings.
Any user can customize programs that use Readline by putting
commands in an inputrc file, conventionally in his home directory.
The name of this
file is taken from the value of the environment variable INPUTRC. If
that variable is unset, the default is `~/.inputrc'. If that
file does not exist or cannot be read, the ultimate default is
`/etc/inputrc'.

When a program which uses the Readline library starts up, the
init file is read, and the key bindings are set.

In addition, the C-x C-r command re-reads this init file, thus
incorporating any changes that you might have made to it.

1.3.1 Readline Init File Syntax

There are only a few basic constructs allowed in the
Readline init file. Blank lines are ignored.
Lines beginning with a `#' are comments.
Lines beginning with a `$' indicate conditional
constructs (see section 1.3.2 Conditional Init Constructs). Other lines
denote variable settings and key bindings.

Variable Settings

You can modify the run-time behavior of Readline by
altering the values of variables in Readline
using the set command within the init file.
The syntax is simple:

set variablevalue

Here, for example, is how to
change from the default Emacs-like key binding to use
vi line editing commands:

set editing-mode vi

Variable names and values, where appropriate, are recognized without regard
to case. Unrecognized variable names are ignored.

Boolean variables (those that can be set to on or off) are set to on if
the value is null or empty, on (case-insensitive), or 1. Any other
value results in the variable being set to off.

A great deal of run-time behavior is changeable with the following
variables.

bell-style

Controls what happens when Readline wants to ring the terminal bell.
If set to `none', Readline never rings the bell. If set to
`visible', Readline uses a visible bell if one is available.
If set to `audible' (the default), Readline attempts to ring
the terminal's bell.

bind-tty-special-chars

If set to `on', Readline attempts to bind the control characters
treated specially by the kernel's terminal driver to their Readline
equivalents.

colored-stats

If set to `on', Readline displays possible completions using different
colors to indicate their file type.
The color definitions are taken from the value of the LS_COLORS
environment variable.
The default is `off'.

comment-begin

The string to insert at the beginning of the line when the
insert-comment command is executed. The default value
is "#".

completion-display-width

The number of screen columns used to display possible matches
when performing completion.
The value is ignored if it is less than 0 or greater than the terminal
screen width.
A value of 0 will cause matches to be displayed one per line.
The default value is -1.

completion-ignore-case

If set to `on', Readline performs filename matching and completion
in a case-insensitive fashion.
The default value is `off'.

completion-map-case

If set to `on', and completion-ignore-case is enabled, Readline
treats hyphens (`-') and underscores (`_') as equivalent when
performing case-insensitive filename matching and completion.

completion-prefix-display-length

The length in characters of the common prefix of a list of possible
completions that is displayed without modification. When set to a
value greater than zero, common prefixes longer than this value are
replaced with an ellipsis when displaying possible completions.

completion-query-items

The number of possible completions that determines when the user is
asked whether the list of possibilities should be displayed.
If the number of possible completions is greater than this value,
Readline will ask the user whether or not he wishes to view
them; otherwise, they are simply listed.
This variable must be set to an integer value greater than or equal to 0.
A negative value means Readline should never ask.
The default limit is 100.

convert-meta

If set to `on', Readline will convert characters with the
eighth bit set to an ASCII key sequence by stripping the eighth
bit and prefixing an ESC character, converting them to a
meta-prefixed key sequence. The default value is `on'.

disable-completion

If set to `On', Readline will inhibit word completion.
Completion characters will be inserted into the line as if they had
been mapped to self-insert. The default is `off'.

editing-mode

The editing-mode variable controls which default set of
key bindings is used. By default, Readline starts up in Emacs editing
mode, where the keystrokes are most similar to Emacs. This variable can be
set to either `emacs' or `vi'.

echo-control-characters

When set to `on', on operating systems that indicate they support it,
readline echoes a character corresponding to a signal generated from the
keyboard. The default is `on'.

enable-keypad

When set to `on', Readline will try to enable the application
keypad when it is called. Some systems need this to enable the
arrow keys. The default is `off'.

enable-meta-key

When set to `on', Readline will try to enable any meta modifier
key the terminal claims to support when it is called. On many terminals,
the meta key is used to send eight-bit characters.
The default is `on'.

expand-tilde

If set to `on', tilde expansion is performed when Readline
attempts word completion. The default is `off'.

history-preserve-point

If set to `on', the history code attempts to place the point (the
current cursor position) at the
same location on each history line retrieved with previous-history
or next-history. The default is `off'.

history-size

Set the maximum number of history entries saved in the history list.
If set to zero, any existing history entries are deleted and no new entries
are saved.
If set to a value less than zero, the number of history entries is not
limited.
By default, the number of history entries is not limited.

horizontal-scroll-mode

This variable can be set to either `on' or `off'. Setting it
to `on' means that the text of the lines being edited will scroll
horizontally on a single screen line when they are longer than the width
of the screen, instead of wrapping onto a new screen line. By default,
this variable is set to `off'.

input-meta

If set to `on', Readline will enable eight-bit input (it
will not clear the eighth bit in the characters it reads),
regardless of what the terminal claims it can support. The
default value is `off'. The name meta-flag is a
synonym for this variable.

isearch-terminators

The string of characters that should terminate an incremental search without
subsequently executing the character as a command (see section 1.2.5 Searching for Commands in the History).
If this variable has not been given a value, the characters ESC and
C-J will terminate an incremental search.

keymap

Sets Readline's idea of the current keymap for key binding commands.
Acceptable keymap names are
emacs,
emacs-standard,
emacs-meta,
emacs-ctlx,
vi,
vi-move,
vi-command, and
vi-insert.
vi is equivalent to vi-command; emacs is
equivalent to emacs-standard. The default value is emacs.
The value of the editing-mode variable also affects the
default keymap.

keyseq-timeout

Specifies the duration Readline will wait for a character when reading an
ambiguous key sequence (one that can form a complete key sequence using
the input read so far, or can take additional input to complete a longer
key sequence).
If no input is received within the timeout, Readline will use the shorter
but complete key sequence.
Readline uses this value to determine whether or not input is
available on the current input source (rl_instream by default).
The value is specified in milliseconds, so a value of 1000 means that
Readline will wait one second for additional input.
If this variable is set to a value less than or equal to zero, or to a
non-numeric value, Readline will wait until another key is pressed to
decide which key sequence to complete.
The default value is 500.

mark-directories

If set to `on', completed directory names have a slash
appended. The default is `on'.

mark-modified-lines

This variable, when set to `on', causes Readline to display an
asterisk (`*') at the start of history lines which have been modified.
This variable is `off' by default.

mark-symlinked-directories

If set to `on', completed names which are symbolic links
to directories have a slash appended (subject to the value of
mark-directories).
The default is `off'.

match-hidden-files

This variable, when set to `on', causes Readline to match files whose
names begin with a `.' (hidden files) when performing filename
completion.
If set to `off', the leading `.' must be
supplied by the user in the filename to be completed.
This variable is `on' by default.

menu-complete-display-prefix

If set to `on', menu completion displays the common prefix of the
list of possible completions (which may be empty) before cycling through
the list. The default is `off'.

output-meta

If set to `on', Readline will display characters with the
eighth bit set directly rather than as a meta-prefixed escape
sequence. The default is `off'.

page-completions

If set to `on', Readline uses an internal more-like pager
to display a screenful of possible completions at a time.
This variable is `on' by default.

print-completions-horizontally

If set to `on', Readline will display completions with matches
sorted horizontally in alphabetical order, rather than down the screen.
The default is `off'.

revert-all-at-newline

If set to `on', Readline will undo all changes to history lines
before returning when accept-line is executed. By default,
history lines may be modified and retain individual undo lists across
calls to readline. The default is `off'.

show-all-if-ambiguous

This alters the default behavior of the completion functions. If
set to `on',
words which have more than one possible completion cause the
matches to be listed immediately instead of ringing the bell.
The default value is `off'.

show-all-if-unmodified

This alters the default behavior of the completion functions in
a fashion similar to show-all-if-ambiguous.
If set to `on',
words which have more than one possible completion without any
possible partial completion (the possible completions don't share
a common prefix) cause the matches to be listed immediately instead
of ringing the bell.
The default value is `off'.

show-mode-in-prompt

If set to `on', add a character to the beginning of the prompt
indicating the editing mode: emacs (`@'), vi command (`:'),
or vi insertion (`+').
The default value is `off'.

skip-completed-text

If set to `on', this alters the default completion behavior when
inserting a single match into the line. It's only active when
performing completion in the middle of a word. If enabled, readline
does not insert characters from the completion that match characters
after point in the word being completed, so portions of the word
following the cursor are not duplicated.
For instance, if this is enabled, attempting completion when the cursor
is after the `e' in `Makefile' will result in `Makefile'
rather than `Makefilefile', assuming there is a single possible
completion.
The default value is `off'.

visible-stats

If set to `on', a character denoting a file's type
is appended to the filename when listing possible
completions. The default is `off'.

Key Bindings

The syntax for controlling key bindings in the init file is
simple. First you need to find the name of the command that you
want to change. The following sections contain tables of the command
name, the default keybinding, if any, and a short description of what
the command does.

Once you know the name of the command, simply place on a line
in the init file the name of the key
you wish to bind the command to, a colon, and then the name of the
command.
There can be no space between the key name and the colon -- that will be
interpreted as part of the key name.
The name of the key can be expressed in different ways, depending on
what you find most comfortable.

In addition to command names, readline allows keys to be bound
to a string that is inserted when the key is pressed (a macro).

In the above example, C-u is bound to the function
universal-argument,
M-DEL is bound to the function backward-kill-word, and
C-o is bound to run the macro
expressed on the right hand side (that is, to insert the text
`> output' into the line).

A number of symbolic character names are recognized while
processing this key binding syntax:
DEL,
ESC,
ESCAPE,
LFD,
NEWLINE,
RET,
RETURN,
RUBOUT,
SPACE,
SPC,
and
TAB.

"keyseq": function-name or macro

keyseq differs from keyname above in that strings
denoting an entire key sequence can be specified, by placing
the key sequence in double quotes. Some GNU Emacs style key
escapes can be used, as in the following example, but the
special character names are not recognized.

In the above example, C-u is again bound to the function
universal-argument (just as it was in the first example),
`C-xC-r' is bound to the function re-read-init-file,
and `ESC[11~' is bound to insert
the text `Function Key 1'.

The following GNU Emacs style escape sequences are available when
specifying key sequences:

\C-

control prefix

\M-

meta prefix

\e

an escape character

\\

backslash

\"

", a double quotation mark

\'

', a single quote or apostrophe

In addition to the GNU Emacs style escape sequences, a second
set of backslash escapes is available:

\a

alert (bell)

\b

backspace

\d

delete

\f

form feed

\n

newline

\r

carriage return

\t

horizontal tab

\v

vertical tab

\nnn

the eight-bit character whose value is the octal value nnn
(one to three digits)

\xHH

the eight-bit character whose value is the hexadecimal value HH
(one or two hex digits)

When entering the text of a macro, single or double quotes must
be used to indicate a macro definition.
Unquoted text is assumed to be a function name.
In the macro body, the backslash escapes described above are expanded.
Backslash will quote any other character in the macro text,
including `"' and `''.
For example, the following binding will make `C-x \'
insert a single `\' into the line:

1.3.2 Conditional Init Constructs

Readline implements a facility similar in spirit to the conditional
compilation features of the C preprocessor which allows key
bindings and variable settings to be performed as the result
of tests. There are four parser directives used.

$if

The $if construct allows bindings to be made based on the
editing mode, the terminal being used, or the application using
Readline. The text of the test extends to the end of the line;
no characters are required to isolate it.

mode

The mode= form of the $if directive is used to test
whether Readline is in emacs or vi mode.
This may be used in conjunction
with the `set keymap' command, for instance, to set bindings in
the emacs-standard and emacs-ctlx keymaps only if
Readline is starting out in emacs mode.

term

The term= form may be used to include terminal-specific
key bindings, perhaps to bind the key sequences output by the
terminal's function keys. The word on the right side of the
`=' is tested against both the full name of the terminal and
the portion of the terminal name before the first `-'. This
allows sun to match both sun and sun-cmd,
for instance.

application

The application construct is used to include
application-specific settings. Each program using the Readline
library sets the application name, and you can test for
a particular value.
This could be used to bind key sequences to functions useful for
a specific program. For instance, the following command adds a
key sequence that quotes the current or previous word in Bash:

This section describes Readline commands that may be bound to key
sequences.
Command names without an accompanying key sequence are unbound by default.

In the following descriptions, point refers to the current cursor
position, and mark refers to a cursor position saved by the
set-mark command.
The text between the point and mark is referred to as the region.

1.4.2 Commands For Manipulating The History

accept-line (Newline or Return)

Accept the line regardless of where the cursor is.
If this line is
non-empty, it may be added to the history list for future recall with
add_history().
If this line is a modified history line, the history line is restored
to its original state.

previous-history (C-p)

Move `back' through the history list, fetching the previous command.

next-history (C-n)

Move `forward' through the history list, fetching the next command.

beginning-of-history (M-<)

Move to the first line in the history.

end-of-history (M->)

Move to the end of the input history, i.e., the line currently
being entered.

reverse-search-history (C-r)

Search backward starting at the current line and moving `up' through
the history as necessary. This is an incremental search.

forward-search-history (C-s)

Search forward starting at the current line and moving `down' through
the the history as necessary. This is an incremental search.

non-incremental-reverse-search-history (M-p)

Search backward starting at the current line and moving `up'
through the history as necessary using a non-incremental search
for a string supplied by the user.

non-incremental-forward-search-history (M-n)

Search forward starting at the current line and moving `down'
through the the history as necessary using a non-incremental search
for a string supplied by the user.

history-search-forward ()

Search forward through the history for the string of characters
between the start of the current line and the point.
The search string must match at the beginning of a history line.
This is a non-incremental search.
By default, this command is unbound.

history-search-backward ()

Search backward through the history for the string of characters
between the start of the current line and the point.
The search string must match at the beginning of a history line.
This is a non-incremental search.
By default, this command is unbound.

history-substr-search-forward ()

Search forward through the history for the string of characters
between the start of the current line and the point.
The search string may match anywhere in a history line.
This is a non-incremental search.
By default, this command is unbound.

history-substr-search-backward ()

Search backward through the history for the string of characters
between the start of the current line and the point.
The search string may match anywhere in a history line.
This is a non-incremental search.
By default, this command is unbound.

yank-nth-arg (M-C-y)

Insert the first argument to the previous command (usually
the second word on the previous line) at point.
With an argument n,
insert the nth word from the previous command (the words
in the previous command begin with word 0). A negative argument
inserts the nth word from the end of the previous command.
Once the argument n is computed, the argument is extracted
as if the `!n' history expansion had been specified.

yank-last-arg (M-. or M-_)

Insert last argument to the previous command (the last word of the
previous history entry).
With a numeric argument, behave exactly like yank-nth-arg.
Successive calls to yank-last-arg move back through the history
list, inserting the last word (or the word specified by the argument to
the first call) of each line in turn.
Any numeric argument supplied to these successive calls determines
the direction to move through the history. A negative argument switches
the direction through the history (back or forward).
The history expansion facilities are used to extract the last argument,
as if the `!$' history expansion had been specified.

1.4.3 Commands For Changing Text

end-of-file (usually C-d)

The character indicating end-of-file as set, for example, by
stty. If this character is read when there are no characters
on the line, and point is at the beginning of the line, Readline
interprets it as the end of input and returns EOF.

delete-char (C-d)

Delete the character at point. If this function is bound to the
same character as the tty EOF character, as C-d
commonly is, see above for the effects.

backward-delete-char (Rubout)

Delete the character behind the cursor. A numeric argument means
to kill the characters instead of deleting them.

forward-backward-delete-char ()

Delete the character under the cursor, unless the cursor is at the
end of the line, in which case the character behind the cursor is
deleted. By default, this is not bound to a key.

quoted-insert (C-q or C-v)

Add the next character typed to the line verbatim. This is
how to insert key sequences like C-q, for example.

tab-insert (M-TAB)

Insert a tab character.

self-insert (a, b, A, 1, !, ...)

Insert yourself.

transpose-chars (C-t)

Drag the character before the cursor forward over
the character at the cursor, moving the
cursor forward as well. If the insertion point
is at the end of the line, then this
transposes the last two characters of the line.
Negative arguments have no effect.

transpose-words (M-t)

Drag the word before point past the word after point,
moving point past that word as well.
If the insertion point is at the end of the line, this transposes
the last two words on the line.

upcase-word (M-u)

Uppercase the current (or following) word. With a negative argument,
uppercase the previous word, but do not move the cursor.

downcase-word (M-l)

Lowercase the current (or following) word. With a negative argument,
lowercase the previous word, but do not move the cursor.

capitalize-word (M-c)

Capitalize the current (or following) word. With a negative argument,
capitalize the previous word, but do not move the cursor.

In overwrite mode, characters bound to self-insert replace
the text at point rather than pushing the text to the right.
Characters bound to backward-delete-char replace the character
before point with a space.

1.4.5 Specifying Numeric Arguments

digit-argument (M-0, M-1, ...M--)

Add this digit to the argument already accumulating, or start a new
argument. M-- starts a negative argument.

universal-argument ()

This is another way to specify an argument.
If this command is followed by one or more digits, optionally with a
leading minus sign, those digits define the argument.
If the command is followed by digits, executing universal-argument
again ends the numeric argument, but is otherwise ignored.
As a special case, if this command is immediately followed by a
character that is neither a digit or minus sign, the argument count
for the next command is multiplied by four.
The argument count is initially one, so executing this function the
first time makes the argument count four, a second time makes the
argument count sixteen, and so on.
By default, this is not bound to a key.

1.4.6 Letting Readline Type For You

complete (TAB)

Attempt to perform completion on the text before point.
The actual completion performed is application-specific.
The default is filename completion.

possible-completions (M-?)

List the possible completions of the text before point.
When displaying completions, Readline sets the number of columns used
for display to the value of completion-display-width, the value of
the environment variable COLUMNS, or the screen width, in that order.

insert-completions (M-*)

Insert all completions of the text before point that would have
been generated by possible-completions.

menu-complete ()

Similar to complete, but replaces the word to be completed
with a single match from the list of possible completions.
Repeated execution of menu-complete steps through the list
of possible completions, inserting each match in turn.
At the end of the list of completions, the bell is rung
(subject to the setting of bell-style)
and the original text is restored.
An argument of n moves n positions forward in the list
of matches; a negative argument may be used to move backward
through the list.
This command is intended to be bound to TAB, but is unbound
by default.

menu-complete-backward ()

Identical to menu-complete, but moves backward through the list
of possible completions, as if menu-complete had been given a
negative argument.

delete-char-or-list ()

Deletes the character under the cursor if not at the beginning or
end of the line (like delete-char).
If at the end of the line, behaves identically to
possible-completions.
This command is unbound by default.

1.4.8 Some Miscellaneous Commands

Read in the contents of the inputrc file, and incorporate
any bindings or variable assignments found there.

abort (C-g)

Abort the current editing command and
ring the terminal's bell (subject to the setting of
bell-style).

do-uppercase-version (M-a, M-b, M-x, ...)

If the metafied character x is lowercase, run the command
that is bound to the corresponding uppercase character.

prefix-meta (ESC)

Metafy the next character typed. This is for keyboards
without a meta key. Typing `ESC f' is equivalent to typing
M-f.

undo (C-_ or C-x C-u)

Incremental undo, separately remembered for each line.

revert-line (M-r)

Undo all changes made to this line. This is like executing the undo
command enough times to get back to the beginning.

tilde-expand (M-~)

Perform tilde expansion on the current word.

set-mark (C-@)

Set the mark to the point. If a
numeric argument is supplied, the mark is set to that position.

exchange-point-and-mark (C-x C-x)

Swap the point with the mark. The current cursor position is set to
the saved position, and the old cursor position is saved as the mark.

character-search (C-])

A character is read and point is moved to the next occurrence of that
character. A negative count searches for previous occurrences.

character-search-backward (M-C-])

A character is read and point is moved to the previous occurrence
of that character. A negative count searches for subsequent
occurrences.

skip-csi-sequence ()

Read enough characters to consume a multi-key sequence such as those
defined for keys like Home and End. Such sequences begin with a
Control Sequence Indicator (CSI), usually ESC-[. If this sequence is
bound to "\e[", keys producing such sequences will have no effect
unless explicitly bound to a readline command, instead of inserting
stray characters into the editing buffer. This is unbound by default,
but usually bound to ESC-[.

insert-comment (M-#)

Without a numeric argument, the value of the comment-begin
variable is inserted at the beginning of the current line.
If a numeric argument is supplied, this command acts as a toggle: if
the characters at the beginning of the line do not match the value
of comment-begin, the value is inserted, otherwise
the characters in comment-begin are deleted from the beginning of
the line.
In either case, the line is accepted as if a newline had been typed.

dump-functions ()

Print all of the functions and their key bindings to the
Readline output stream. If a numeric argument is supplied,
the output is formatted in such a way that it can be made part
of an inputrc file. This command is unbound by default.

dump-variables ()

Print all of the settable variables and their values to the
Readline output stream. If a numeric argument is supplied,
the output is formatted in such a way that it can be made part
of an inputrc file. This command is unbound by default.

dump-macros ()

Print all of the Readline key sequences bound to macros and the
strings they output. If a numeric argument is supplied,
the output is formatted in such a way that it can be made part
of an inputrc file. This command is unbound by default.

1.5 Readline vi Mode

While the Readline library does not have a full set of vi
editing functions, it does contain enough to allow simple editing
of the line. The Readline vi mode behaves as specified in
the POSIX standard.

In order to switch interactively between emacs and vi
editing modes, use the command M-C-j (bound to emacs-editing-mode
when in vi mode and to vi-editing-mode in emacs mode).
The Readline default is emacs mode.

When you enter a line in vi mode, you are already placed in
`insertion' mode, as if you had typed an `i'. Pressing ESC
switches you into `command' mode, where you can edit the text of the
line with the standard vi movement keys, move to previous
history lines with `k' and subsequent lines with `j', and
so forth.

This document describes the GNU Readline Library, a utility for aiding
in the consistency of user interface across discrete programs that need
to provide a command line interface.

Copyright (C) 1988--2014 Free Software Foundation, Inc.

Permission is granted to make and distribute verbatim copies of
this manual provided the copyright notice and this permission notice
pare preserved on all copies.

Permission is granted to copy and distribute modified versions of this
manual under the conditions for verbatim copying, provided that the entire
resulting derived work is distributed under the terms of a permission
notice identical to this one.

Permission is granted to copy and distribute translations of this manual
into another language, under the above conditions for modified versions,
except that this permission notice may be stated in a translation approved
by the Foundation.

2. Programming with GNU Readline

This chapter describes the interface between the GNU Readline Library and
other programs. If you are a programmer, and you wish to include the
features found in GNU Readline
such as completion, line editing, and interactive history manipulation
in your own programs, this section is for you.

2.1 Basic Behavior

Many programs provide a command line interface, such as mail,
ftp, and sh. For such programs, the default behaviour of
Readline is sufficient. This section describes how to use Readline in
the simplest way possible, perhaps to replace calls in your code to
gets() or fgets().

The function readline() prints a prompt prompt
and then reads and returns a single line of text from the user.
If prompt is NULL or the empty string, no prompt is displayed.
The line readline returns is allocated with malloc();
the caller should free() the line when it has finished with it.
The declaration for readline in ANSI C is

char *readline (const char *prompt);

So, one might say

char *line = readline ("Enter a line: ");

in order to read a line of text from the user.
The line returned has the final newline removed, so only the
text remains.

If readline encounters an EOF while reading the line, and the
line is empty at that point, then (char *)NULL is returned.
Otherwise, the line is ended just as if a newline had been typed.

If you want the user to be able to get at the line later, (with
C-p for example), you must call add_history() to save the
line away in a history list of such lines.

add_history (line);

For full details on the GNU History Library, see the associated manual.

It is preferable to avoid saving empty lines on the history list, since
users rarely have a burning need to reuse a blank line. Here is
a function which usefully replaces the standard gets() library
function, and has the advantage of no static buffer to overflow:

/* A static variable for holding the line. */
static char *line_read = (char *)NULL;
/* Read a string, and return a pointer to it.
Returns NULL on EOF. */
char *
rl_gets ()
{
/* If the buffer has already been allocated,
return the memory to the free pool. */
if (line_read)
{
free (line_read);
line_read = (char *)NULL;
}
/* Get a line from the user. */
line_read = readline ("");
/* If the line has any text in it,
save it on the history. */
if (line_read && *line_read)
add_history (line_read);
return (line_read);
}

This function gives the user the default behaviour of TAB
completion: completion on file names. If you do not want Readline to
complete on filenames, you can change the binding of the TAB key
with rl_bind_key().

int rl_bind_key (int key, rl_command_func_t *function);

rl_bind_key() takes two arguments: key is the character that
you want to bind, and function is the address of the function to
call when key is pressed. Binding TAB to rl_insert()
makes TAB insert itself.
rl_bind_key() returns non-zero if key is not a valid
ASCII character code (between 0 and 255).

Thus, to disable the default TAB behavior, the following suffices:

rl_bind_key ('\t', rl_insert);

This code should be executed once at the start of your program; you
might write a function called initialize_readline() which
performs this and other desired initializations, such as installing
custom completers (see section 2.6 Custom Completers).

2.2 Custom Functions

Readline provides many functions for manipulating the text of
the line, but it isn't possible to anticipate the needs of all
programs. This section describes the various functions and variables
defined within the Readline library which allow a user program to add
customized functionality to Readline.

Before declaring any functions that customize Readline's behavior, or
using any functionality Readline provides in other code, an
application writer should include the file <readline/readline.h>
in any file that uses Readline's features. Since some of the definitions
in readline.h use the stdio library, the file
<stdio.h> should be included before readline.h.

readline.h defines a C preprocessor variable that should
be treated as an integer, RL_READLINE_VERSION, which may
be used to conditionally compile application code depending on
the installed Readline version. The value is a hexadecimal
encoding of the major and minor version numbers of the library,
of the form 0xMMmm. MM is the two-digit major
version number; mm is the two-digit minor version number.
For Readline 4.2, for example, the value of
RL_READLINE_VERSION would be 0x0402.

2.2.1 Readline Typedefs

For readability, we declare a number of new object types, all pointers
to functions.

The reason for declaring these new types is to make it easier to write
code describing pointers to C functions with appropriately prototyped
arguments and return values.

For instance, say we want to declare a variable func as a pointer
to a function which takes two int arguments and returns an
int (this is the type of all of the Readline bindable functions).
Instead of the classic C declaration

2.2.2 Writing a New Function

In order to write new functions for Readline, you need to know the
calling conventions for keyboard-invoked functions, and the names of the
variables that describe the current state of the line read so far.

The calling sequence for a command foo looks like

int foo (int count, int key)

where count is the numeric argument (or 1 if defaulted) and
key is the key that invoked this function.

It is completely up to the function as to what should be done with the
numeric argument. Some functions use it as a repeat count, some
as a flag, and others to choose alternate behavior (refreshing the current
line as opposed to refreshing the screen, for example). Some choose to
ignore it. In general, if a
function uses the numeric argument as a repeat count, it should be able
to do something useful with both negative and positive arguments.
At the very least, it should be aware that it can be passed a
negative argument.

A command function should return 0 if its action completes successfully,
and a non-zero value if some error occurs.
This is the convention obeyed by all of the builtin Readline bindable
command functions.

2.3 Readline Variables

These variables are available to function writers.

Variable: char * rl_line_buffer

This is the line gathered so far. You are welcome to modify the
contents of the line, but see 2.4.5 Allowing Undoing. The
function rl_extend_line_buffer is available to increase
the memory allocated to rl_line_buffer.

Variable: int rl_point

The offset of the current cursor position in rl_line_buffer
(the point).

Variable: int rl_end

The number of characters present in rl_line_buffer. When
rl_point is at the end of the line, rl_point and
rl_end are equal.

Variable: int rl_mark

The mark (saved position) in the current line. If set, the mark
and point define a region.

Variable: int rl_done

Setting this to a non-zero value causes Readline to return the current
line immediately.

Variable: int rl_num_chars_to_read

Setting this to a positive value before calling readline() causes
Readline to return after accepting that many characters, rather
than reading up to a character bound to accept-line.

Variable: int rl_pending_input

Setting this to a value makes it the next keystroke read. This is a
way to stuff a single character into the input stream.

Variable: int rl_dispatching

Set to a non-zero value if a function is being called from a key binding;
zero otherwise. Application functions can test this to discover whether
they were called directly or by Readline's dispatching mechanism.

Variable: int rl_erase_empty_line

Setting this to a non-zero value causes Readline to completely erase
the current line, including any prompt, any time a newline is typed as
the only character on an otherwise-empty line. The cursor is moved to
the beginning of the newly-blank line.

Variable: char * rl_prompt

The prompt Readline uses. This is set from the argument to
readline(), and should not be assigned to directly.
The rl_set_prompt() function (see section 2.4.6 Redisplay) may
be used to modify the prompt string after calling readline().

Variable: char * rl_display_prompt

The string displayed as the prompt. This is usually identical to
rl_prompt, but may be changed temporarily by functions that
use the prompt string as a message area, such as incremental search.

Variable: int rl_already_prompted

If an application wishes to display the prompt itself, rather than have
Readline do it the first time readline() is called, it should set
this variable to a non-zero value after displaying the prompt.
The prompt must also be passed as the argument to readline() so
the redisplay functions can update the display properly.
The calling application is responsible for managing the value; Readline
never sets it.

Variable: const char * rl_library_version

The version number of this revision of the library.

Variable: int rl_readline_version

An integer encoding the current version of the library. The encoding is
of the form 0xMMmm, where MM is the two-digit major version
number, and mm is the two-digit minor version number.
For example, for Readline-4.2, rl_readline_version would have the
value 0x0402.

Variable: int rl_gnu_readline_p

Always set to 1, denoting that this is GNU readline rather than some
emulation.

Variable: const char * rl_terminal_name

The terminal type, used for initialization. If not set by the application,
Readline sets this to the value of the TERM environment variable
the first time it is called.

Variable: const char * rl_readline_name

This variable is set to a unique name by each application using Readline.
The value allows conditional parsing of the inputrc file
(see section 1.3.2 Conditional Init Constructs).

Variable: FILE * rl_instream

The stdio stream from which Readline reads input.
If NULL, Readline defaults to stdin.

Variable: FILE * rl_outstream

The stdio stream to which Readline performs output.
If NULL, Readline defaults to stdout.

Variable: int rl_prefer_env_winsize

If non-zero, Readline gives values found in the LINES and
COLUMNS environment variables greater precedence than values fetched
from the kernel when computing the screen dimensions.

Variable: rl_command_func_t * rl_last_func

The address of the last command function Readline executed. May be used to
test whether or not a function is being executed twice in succession, for
example.

Variable: rl_hook_func_t * rl_startup_hook

If non-zero, this is the address of a function to call just
before readline prints the first prompt.

Variable: rl_hook_func_t * rl_pre_input_hook

If non-zero, this is the address of a function to call after
the first prompt has been printed and just before readline
starts reading input characters.

Variable: rl_hook_func_t * rl_event_hook

If non-zero, this is the address of a function to call periodically
when Readline is waiting for terminal input.
By default, this will be called at most ten times a second if there
is no keyboard input.

Variable: rl_getc_func_t * rl_getc_function

If non-zero, Readline will call indirectly through this pointer
to get a character from the input stream. By default, it is set to
rl_getc, the default Readline character input function
(see section 2.4.8 Character Input).
In general, an application that sets rl_getc_function should consider
setting rl_input_available_hook as well.

Variable: rl_hook_func_t * rl_signal_event_hook

If non-zero, this is the address of a function to call if a read system
call is interrupted when Readline is reading terminal input.

Variable: rl_hook_func_t * rl_input_available_hook

If non-zero, Readline will use this function's return value when it needs
to determine whether or not there is available input on the current input
source.
The default hook checks rl_instream; if an application is using a
different input source, it should set the hook appropriately.
Readline queries for available input when implementing intra-key-sequence
timeouts during input and incremental searches.
This may use an application-specific timeout before returning a value;
Readline uses the value passed to rl_set_keyboard_input_timeout()
or the value of the user-settable keyseq-timeout variable.
This is designed for use by applications using Readline's callback interface
(see section 2.4.12 Alternate Interface), which may not use the traditional
read(2) and file descriptor interface, or other applications using
a different input mechanism.
If an application uses an input mechanism or hook that can potentially exceed
the value of keyseq-timeout, it should increase the timeout or set
this hook appropriately even when not using the callback interface.
In general, an application that sets rl_getc_function should consider
setting rl_input_available_hook as well.

Variable: rl_voidfunc_t * rl_redisplay_function

If non-zero, Readline will call indirectly through this pointer
to update the display with the current contents of the editing buffer.
By default, it is set to rl_redisplay, the default Readline
redisplay function (see section 2.4.6 Redisplay).

Variable: rl_vintfunc_t * rl_prep_term_function

If non-zero, Readline will call indirectly through this pointer
to initialize the terminal. The function takes a single argument, an
int flag that says whether or not to use eight-bit characters.
By default, this is set to rl_prep_terminal
(see section 2.4.9 Terminal Management).

Variable: rl_voidfunc_t * rl_deprep_term_function

If non-zero, Readline will call indirectly through this pointer
to reset the terminal. This function should undo the effects of
rl_prep_term_function.
By default, this is set to rl_deprep_terminal
(see section 2.4.9 Terminal Management).

Variable: Keymap rl_executing_keymap

This variable is set to the keymap (see section 2.4.2 Selecting a Keymap) in which the
currently executing readline function was found.

The key that caused the dispatch to the currently-executing Readline function.

Variable: char * rl_executing_keyseq

The full key sequence that caused the dispatch to the currently-executing
Readline function.

Variable: int rl_key_sequence_length

The number of characters in rl_executing_keyseq.

Variable: int rl_readline_state

A variable with bit values that encapsulate the current Readline state.
A bit is set with the RL_SETSTATE macro, and unset with the
RL_UNSETSTATE macro. Use the RL_ISSTATE macro to test
whether a particular state bit is set. Current state bits include:

RL_STATE_NONE

Readline has not yet been called, nor has it begun to initialize.

RL_STATE_INITIALIZING

Readline is initializing its internal data structures.

RL_STATE_INITIALIZED

Readline has completed its initialization.

RL_STATE_TERMPREPPED

Readline has modified the terminal modes to do its own input and redisplay.

RL_STATE_READCMD

Readline is reading a command from the keyboard.

RL_STATE_METANEXT

Readline is reading more input after reading the meta-prefix character.

RL_STATE_DISPATCHING

Readline is dispatching to a command.

RL_STATE_MOREINPUT

Readline is reading more input while executing an editing command.

RL_STATE_ISEARCH

Readline is performing an incremental history search.

RL_STATE_NSEARCH

Readline is performing a non-incremental history search.

RL_STATE_SEARCH

Readline is searching backward or forward through the history for a string.

RL_STATE_NUMERICARG

Readline is reading a numeric argument.

RL_STATE_MACROINPUT

Readline is currently getting its input from a previously-defined keyboard
macro.

2.4.1 Naming a Function

The user can dynamically change the bindings of keys while using
Readline. This is done by representing the function with a descriptive
name. The user is able to type the descriptive name when referring to
the function. Thus, in an init file, one might find

Meta-Rubout: backward-kill-word

This binds the keystroke Meta-Rubout to the function
descriptively named backward-kill-word. You, as the
programmer, should bind the functions you write to descriptive names as
well. Readline provides a function for doing that:

Add name to the list of named functions. Make function be
the function that gets called. If key is not -1, then bind it to
function using rl_bind_key().

Using this function alone is sufficient for most applications.
It is the recommended way to add a few functions to the default
functions that Readline has built in.
If you need to do something other than adding a function to Readline,
you may need to use the underlying functions described below.

2.4.2 Selecting a Keymap

Key bindings take place on a keymap. The keymap is the
association between the keys that the user types and the functions that
get run. You can make your own keymaps, copy existing keymaps, and tell
Readline which keymap to use.

Function: Keymap rl_make_bare_keymap(void)

Returns a new, empty keymap. The space for the keymap is allocated with
malloc(); the caller should free it by calling
rl_free_keymap() when done.

Function: Keymap rl_copy_keymap(Keymap map)

Return a new keymap which is a copy of map.

Function: Keymap rl_make_keymap(void)

Return a new keymap with the printing characters bound to rl_insert,
the lowercase Meta characters bound to run their equivalents, and
the Meta digits bound to produce numeric arguments.

Function: void rl_discard_keymap(Keymap keymap)

Free the storage associated with the data in keymap.
The caller should free keymap.

Function: void rl_free_keymap(Keymap keymap)

Free all storage associated with keymap. This calls
rl_discard_keymap to free subordindate keymaps and macros.

Readline has several internal keymaps. These functions allow you to
change which keymap is active.

Function: Keymap rl_get_keymap(void)

Returns the currently active keymap.

Function: void rl_set_keymap(Keymap keymap)

Makes keymap the currently active keymap.

Function: Keymap rl_get_keymap_by_name(const char *name)

Return the keymap matching name. name is one which would
be supplied in a set keymap inputrc line (see section 1.3 Readline Init File).

Function: char * rl_get_keymap_name(Keymap keymap)

Return the name matching keymap. name is one which would
be supplied in a set keymap inputrc line (see section 1.3 Readline Init File).

2.4.3 Binding Keys

Key sequences are associate with functions through the keymap.
Readline has several internal keymaps: emacs_standard_keymap,
emacs_meta_keymap, emacs_ctlx_keymap,
vi_movement_keymap, and vi_insertion_keymap.
emacs_standard_keymap is the default, and the examples in
this manual assume that.

Since readline() installs a set of default key bindings the first
time it is called, there is always the danger that a custom binding
installed before the first call to readline() will be overridden.
An alternate mechanism is to install custom key bindings in an
initialization function assigned to the rl_startup_hook variable
(see section 2.3 Readline Variables).

These functions manage key bindings.

Function: int rl_bind_key(int key, rl_command_func_t *function)

Binds key to function in the currently active keymap.
Returns non-zero in the case of an invalid key.

Bind the key sequence represented by the string keyseq to the function
function, beginning in the current keymap.
This makes new keymaps as necessary.
The return value is non-zero if keyseq is invalid.

Bind the key sequence represented by the string keyseq to the function
function. This makes new keymaps as necessary.
Initial bindings are performed in map.
The return value is non-zero if keyseq is invalid.

Bind the key sequence represented by the string keyseq to the arbitrary
pointer data. type says what kind of data is pointed to by
data; this can be a function (ISFUNC), a macro
(ISMACR), or a keymap (ISKMAP). This makes new keymaps as
necessary. The initial keymap in which to do bindings is map.

Function: int rl_parse_and_bind(char *line)

Parse line as if it had been read from the inputrc file and
perform any key bindings and variable assignments found
(see section 1.3 Readline Init File).

Return the function invoked by keyseq in keymap map.
If map is NULL, the current keymap is used. If type is
not NULL, the type of the object is returned in the int variable
it points to (one of ISFUNC, ISKMAP, or ISMACR).

Function: char ** rl_invoking_keyseqs(rl_command_func_t *function)

Return an array of strings representing the key sequences used to
invoke function in the current keymap.

Return an array of strings representing the key sequences used to
invoke function in the keymap map.

Function: void rl_function_dumper(int readable)

Print the readline function names and the key sequences currently
bound to them to rl_outstream. If readable is non-zero,
the list is formatted in such a way that it can be made part of an
inputrc file and re-read.

Function: void rl_list_funmap_names(void)

Print the names of all bindable Readline functions to rl_outstream.

Function: const char ** rl_funmap_names(void)

Return a NULL terminated array of known function names. The array is
sorted. The array itself is allocated, but not the strings inside. You
should free the array, but not the pointers, using free or
rl_free when you are done.

2.4.5 Allowing Undoing

Supporting the undo command is a painless thing, and makes your
functions much more useful. It is certainly easy to try
something if you know you can undo it.

If your function simply inserts text once, or deletes text once, and
uses rl_insert_text() or rl_delete_text() to do it, then
undoing is already done for you automatically.

If you do multiple insertions or multiple deletions, or any combination
of these operations, you should group them together into one operation.
This is done with rl_begin_undo_group() and
rl_end_undo_group().

The types of events that can be undone are:

enum undo_code { UNDO_DELETE, UNDO_INSERT, UNDO_BEGIN, UNDO_END };

Notice that UNDO_DELETE means to insert some text, and
UNDO_INSERT means to delete some text. That is, the undo code
tells what to undo, not how to undo it. UNDO_BEGIN and
UNDO_END are tags added by rl_begin_undo_group() and
rl_end_undo_group().

Function: int rl_begin_undo_group(void)

Begins saving undo information in a group construct. The undo
information usually comes from calls to rl_insert_text() and
rl_delete_text(), but could be the result of calls to
rl_add_undo().

Function: int rl_end_undo_group(void)

Closes the current undo group started with rl_begin_undo_group
(). There should be one call to rl_end_undo_group()
for each call to rl_begin_undo_group().

Remember how to undo an event (according to what). The affected
text runs from start to end, and encompasses text.

Function: void rl_free_undo_list(void)

Free the existing undo list.

Function: int rl_do_undo(void)

Undo the first thing on the undo list. Returns 0 if there was
nothing to undo, non-zero if something was undone.

Finally, if you neither insert nor delete text, but directly modify the
existing text (e.g., change its case), call rl_modifying()
once, just before you modify the text. You must supply the indices of
the text range that you are going to modify.

Function: int rl_modifying(int start, int end)

Tell Readline to save the text between start and end as a
single undo unit. It is assumed that you will subsequently modify
that text.

2.4.6 Redisplay

Change what's displayed on the screen to reflect the current contents
of rl_line_buffer.

Function: int rl_forced_update_display(void)

Force the line to be updated and redisplayed, whether or not
Readline thinks the screen display is correct.

Function: int rl_on_new_line(void)

Tell the update functions that we have moved onto a new (empty) line,
usually after outputting a newline.

Function: int rl_on_new_line_with_prompt(void)

Tell the update functions that we have moved onto a new line, with
rl_prompt already displayed.
This could be used by applications that want to output the prompt string
themselves, but still need Readline to know the prompt string length for
redisplay.
It should be used after setting rl_already_prompted.

Function: int rl_reset_line_state(void)

Reset the display state to a clean state and redisplay the current line
starting on a new line.

Function: int rl_crlf(void)

Move the cursor to the start of the next screen line.

Function: int rl_show_char(int c)

Display character c on rl_outstream.
If Readline has not been set to display meta characters directly, this
will convert meta characters to a meta-prefixed key sequence.
This is intended for use by applications which wish to do their own
redisplay.

Function: int rl_message(const char *, ...)

The arguments are a format string as would be supplied to printf,
possibly containing conversion specifications such as `%d', and
any additional arguments necessary to satisfy the conversion specifications.
The resulting string is displayed in the echo area. The echo area
is also used to display numeric arguments and search strings.
You should call rl_save_prompt to save the prompt information
before calling this function.

Function: int rl_clear_message(void)

Clear the message in the echo area. If the prompt was saved with a call to
rl_save_prompt before the last call to rl_message,
call rl_restore_prompt before calling this function.

Function: void rl_save_prompt(void)

Save the local Readline prompt display state in preparation for
displaying a new message in the message area with rl_message().

Function: void rl_restore_prompt(void)

Restore the local Readline prompt display state saved by the most
recent call to rl_save_prompt.
if rl_save_prompt was called to save the prompt before a call
to rl_message, this function should be called before the
corresponding call to rl_clear_message.

Function: int rl_expand_prompt(char *prompt)

Expand any special character sequences in prompt and set up the
local Readline prompt redisplay variables.
This function is called by readline(). It may also be called to
expand the primary prompt if the rl_on_new_line_with_prompt()
function or rl_already_prompted variable is used.
It returns the number of visible characters on the last line of the
(possibly multi-line) prompt.
Applications may indicate that the prompt contains characters that take
up no physical screen space when displayed by bracketing a sequence of
such characters with the special markers RL_PROMPT_START_IGNORE
and RL_PROMPT_END_IGNORE (declared in `readline.h'. This may
be used to embed terminal-specific escape sequences in prompts.

Function: int rl_set_prompt(const char *prompt)

Make Readline use prompt for subsequent redisplay. This calls
rl_expand_prompt() to expand the prompt and sets rl_prompt
to the result.

2.4.7 Modifying Text

Insert text into the line at the current cursor position.
Returns the number of characters inserted.

Function: int rl_delete_text(int start, int end)

Delete the text between start and end in the current line.
Returns the number of characters deleted.

Function: char * rl_copy_text(int start, int end)

Return a copy of the text between start and end in
the current line.

Function: int rl_kill_text(int start, int end)

Copy the text between start and end in the current line
to the kill ring, appending or prepending to the last kill if the
last command was a kill command. The text is deleted.
If start is less than end,
the text is appended, otherwise prepended. If the last command was
not a kill, a new kill ring slot is used.

Function: int rl_push_macro_input(char *macro)

Cause macro to be inserted into the line, as if it had been invoked
by a key bound to a macro. Not especially useful; use
rl_insert_text() instead.

2.4.8 Character Input

Function: int rl_read_key(void)

Return the next character available from Readline's current input stream.
This handles input inserted into
the input stream via rl_pending_input (see section 2.3 Readline Variables)
and rl_stuff_char(), macros, and characters read from the keyboard.
While waiting for input, this function will call any function assigned to
the rl_event_hook variable.

Function: int rl_getc(FILE *stream)

Return the next character available from stream, which is assumed to
be the keyboard.

Function: int rl_stuff_char(int c)

Insert c into the Readline input stream. It will be "read"
before Readline attempts to read characters from the terminal with
rl_read_key(). Up to 512 characters may be pushed back.
rl_stuff_char returns 1 if the character was successfully inserted;
0 otherwise.

Function: int rl_execute_next(int c)

Make c be the next command to be executed when rl_read_key()
is called. This sets rl_pending_input.

Function: int rl_clear_pending_input(void)

Unset rl_pending_input, effectively negating the effect of any
previous call to rl_execute_next(). This works only if the
pending input has not already been read with rl_read_key().

Function: int rl_set_keyboard_input_timeout(int u)

While waiting for keyboard input in rl_read_key(), Readline will
wait for u microseconds for input before calling any function
assigned to rl_event_hook. u must be greater than or equal
to zero (a zero-length timeout is equivalent to a poll).
The default waiting period is one-tenth of a second.
Returns the old timeout value.

2.4.9 Terminal Management

Function: void rl_prep_terminal(int meta_flag)

Modify the terminal settings for Readline's use, so readline()
can read a single character at a time from the keyboard.
The meta_flag argument should be non-zero if Readline should
read eight-bit input.

Function: void rl_deprep_terminal(void)

Undo the effects of rl_prep_terminal(), leaving the terminal in
the state in which it was before the most recent call to
rl_prep_terminal().

Function: void rl_tty_set_default_bindings(Keymap kmap)

Read the operating system's terminal editing characters (as would be
displayed by stty) to their Readline equivalents.
The bindings are performed in kmap.

Function: void rl_tty_unset_default_bindings(Keymap kmap)

Reset the bindings manipulated by rl_tty_set_default_bindings so
that the terminal editing characters are bound to rl_insert.
The bindings are performed in kmap.

Function: int rl_reset_terminal(const char *terminal_name)

Reinitialize Readline's idea of the terminal settings using
terminal_name as the terminal type (e.g., vt100).
If terminal_name is NULL, the value of the TERM
environment variable is used.

2.4.10 Utility Functions

Save a snapshot of Readline's internal state to sp.
The contents of the readline_state structure are documented
in `readline.h'.
The caller is responsible for allocating the structure.

Function: int rl_restore_state(struct readline_state *sp)

Restore Readline's internal state to that stored in sp, which must
have been saved by a call to rl_save_state.
The contents of the readline_state structure are documented
in `readline.h'.
The caller is responsible for freeing the structure.

Function: void rl_free(void *mem)

Deallocate the memory pointed to by mem. mem must have been
allocated by malloc.

Function: void rl_replace_line(const char *text, int clear_undo)

Replace the contents of rl_line_buffer with text.
The point and mark are preserved, if possible.
If clear_undo is non-zero, the undo list associated with the
current line is cleared.

Function: void rl_extend_line_buffer(int len)

Ensure that rl_line_buffer has enough space to hold len
characters, possibly reallocating it if necessary.

Function: int rl_initialize(void)

Initialize or re-initialize Readline's internal state.
It's not strictly necessary to call this; readline() calls it before
reading any input.

A convenience function for displaying a list of strings in
columnar format on Readline's output stream. matches is the list
of strings, in argv format, such as a list of completion matches.
len is the number of strings in matches, and max
is the length of the longest string in matches. This function uses
the setting of print-completions-horizontally to select how the
matches are displayed (see section 1.3.1 Readline Init File Syntax).
When displaying completions, this function sets the number of columns used
for display to the value of completion-display-width, the value of
the environment variable COLUMNS, or the screen width, in that order.

The following are implemented as macros, defined in chardefs.h.
Applications should refrain from using them.

Function: int _rl_uppercase_p(int c)

Return 1 if c is an uppercase alphabetic character.

Function: int _rl_lowercase_p(int c)

Return 1 if c is a lowercase alphabetic character.

Function: int _rl_digit_p(int c)

Return 1 if c is a numeric character.

Function: int _rl_to_upper(int c)

If c is a lowercase alphabetic character, return the corresponding
uppercase character.

Function: int _rl_to_lower(int c)

If c is an uppercase alphabetic character, return the corresponding
lowercase character.

2.4.11 Miscellaneous Functions

Bind the key sequence keyseq to invoke the macro macro.
The binding is performed in map. When keyseq is invoked, the
macro will be inserted into the line. This function is deprecated;
use rl_generic_bind() instead.

Function: void rl_macro_dumper(int readable)

Print the key sequences bound to macros and their values, using
the current keymap, to rl_outstream.
If readable is non-zero, the list is formatted in such a way
that it can be made part of an inputrc file and re-read.

Make the Readline variable variable have value.
This behaves as if the readline command
`set variablevalue' had been executed in an inputrc
file (see section 1.3.1 Readline Init File Syntax).

Function: char * rl_variable_value(const char *variable)

Return a string representing the value of the Readline variable variable.
For boolean variables, this string is either `on' or `off'.

Function: void rl_variable_dumper(int readable)

Print the readline variable names and their current values
to rl_outstream.
If readable is non-zero, the list is formatted in such a way
that it can be made part of an inputrc file and re-read.

Function: int rl_set_paren_blink_timeout(int u)

Set the time interval (in microseconds) that Readline waits when showing
a balancing character when blink-matching-paren has been enabled.

Function: char * rl_get_termcap(const char *cap)

Retrieve the string value of the termcap capability cap.
Readline fetches the termcap entry for the current terminal name and
uses those capabilities to move around the screen line and perform other
terminal-specific operations, like erasing a line. Readline does not
use all of a terminal's capabilities, and this function will return
values for only those capabilities Readline uses.

Function: void rl_clear_history(void)

Clear the history list by deleting all of the entries, in the same manner
as the History library's clear_history() function.
This differs from clear_history because it frees private data
Readline saves in the history list.

2.4.12 Alternate Interface

An alternate interface is available to plain readline(). Some
applications need to interleave keyboard I/O with file, device, or
window system I/O, typically by using a main loop to select()
on various file descriptors. To accommodate this need, readline can
also be invoked as a `callback' function from an event loop. There
are functions available to make this easy.

Set up the terminal for readline I/O and display the initial
expanded value of prompt. Save the value of lhandler to
use as a handler function to call when a complete line of input has been
entered.
The handler function receives the text of the line as an argument.

Function: void rl_callback_read_char(void)

Whenever an application determines that keyboard input is available, it
should call rl_callback_read_char(), which will read the next
character from the current input source.
If that character completes the line, rl_callback_read_char will
invoke the lhandler function installed by
rl_callback_handler_install to process the line.
Before calling the lhandler function, the terminal settings are
reset to the values they had before calling
rl_callback_handler_install.
If the lhandler function returns,
and the line handler remains installed,
the terminal settings are modified for Readline's use again.
EOF is indicated by calling lhandler with a
NULL line.

Function: void rl_callback_handler_remove(void)

Restore the terminal to its initial state and remove the line handler.
This may be called from within a callback as well as independently.
If the lhandler installed by rl_callback_handler_install
does not exit the program, either this function or the function referred
to by the value of rl_deprep_term_function should be called before
the program exits to reset the terminal settings.

2.4.13 A Readline Example

Here is a function which changes lowercase characters to their uppercase
equivalents, and uppercase characters to lowercase. If
this function was bound to `M-c', then typing `M-c' would
change the case of the character under point. Typing `M-1 0 M-c'
would change the case of the following 10 characters, leaving the cursor on
the last character changed.

2.4.14 Alternate Interface Example

Here is a complete program that illustrates Readline's alternate interface.
It reads lines from the terminal and displays them, providing the
standard history and TAB completion functions.
It understands the EOF character or "exit" to exit the program.

2.5 Readline Signal Handling

Signals are asynchronous events sent to a process by the Unix kernel,
sometimes on behalf of another process. They are intended to indicate
exceptional events, like a user pressing the interrupt key on his terminal,
or a network connection being broken. There is a class of signals that can
be sent to the process currently reading input from the keyboard. Since
Readline changes the terminal attributes when it is called, it needs to
perform special processing when such a signal is received in order to
restore the terminal to a sane state, or provide application writers with
functions to do so manually.

Readline contains an internal signal handler that is installed for a
number of signals (SIGINT, SIGQUIT, SIGTERM,
SIGHUP,
SIGALRM, SIGTSTP, SIGTTIN, and SIGTTOU).
When one of these signals is received, the signal handler
will reset the terminal attributes to those that were in effect before
readline() was called, reset the signal handling to what it was
before readline() was called, and resend the signal to the calling
application.
If and when the calling application's signal handler returns, Readline
will reinitialize the terminal and continue to accept input.
When a SIGINT is received, the Readline signal handler performs
some additional work, which will cause any partially-entered line to be
aborted (see the description of rl_free_line_state() below).

There is an additional Readline signal handler, for SIGWINCH, which
the kernel sends to a process whenever the terminal's size changes (for
example, if a user resizes an xterm). The Readline SIGWINCH
handler updates Readline's internal screen size information, and then calls
any SIGWINCH signal handler the calling application has installed.
Readline calls the application's SIGWINCH signal handler without
resetting the terminal to its original state. If the application's signal
handler does more than update its idea of the terminal size and return (for
example, a longjmp back to a main processing loop), it must
call rl_cleanup_after_signal() (described below), to restore the
terminal state.

Readline provides two variables that allow application writers to
control whether or not it will catch certain signals and act on them
when they are received. It is important that applications change the
values of these variables only when calling readline(), not in
a signal handler, so Readline's internal signal state is not corrupted.

Variable: int rl_catch_signals

If this variable is non-zero, Readline will install signal handlers for
SIGINT, SIGQUIT, SIGTERM, SIGHUP, SIGALRM,
SIGTSTP, SIGTTIN, and SIGTTOU.

The default value of rl_catch_signals is 1.

Variable: int rl_catch_sigwinch

If this variable is set to a non-zero value,
Readline will install a signal handler for SIGWINCH.

The default value of rl_catch_sigwinch is 1.

Variable: int rl_change_environment

If this variable is set to a non-zero value,
and Readline is handling SIGWINCH, Readline will modify the
LINES and COLUMNS environment variables upon receipt of a
SIGWINCH

The default value of rl_change_environment is 1.

If an application does not wish to have Readline catch any signals, or
to handle signals other than those Readline catches (SIGHUP,
for example),
Readline provides convenience functions to do the necessary terminal
and internal state cleanup upon receipt of a signal.

Function: void rl_cleanup_after_signal(void)

This function will reset the state of the terminal to what it was before
readline() was called, and remove the Readline signal handlers for
all signals, depending on the values of rl_catch_signals and
rl_catch_sigwinch.

Function: void rl_free_line_state(void)

This will free any partial state associated with the current input line
(undo information, any partial history entry, any partially-entered
keyboard macro, and any partially-entered numeric argument). This
should be called before rl_cleanup_after_signal(). The
Readline signal handler for SIGINT calls this to abort the
current input line.

Function: void rl_reset_after_signal(void)

This will reinitialize the terminal and reinstall any Readline signal
handlers, depending on the values of rl_catch_signals and
rl_catch_sigwinch.

If an application does not wish Readline to catch SIGWINCH, it may
call rl_resize_terminal() or rl_set_screen_size() to force
Readline to update its idea of the terminal size when a SIGWINCH
is received.

Function: void rl_echo_signal_char(int sig)

If an application wishes to install its own signal handlers, but still
have readline display characters that generate signals, calling this
function with sig set to SIGINT, SIGQUIT, or
SIGTSTP will display the character generating that signal.

2.6 Custom Completers

Typically, a program that reads commands from the user has a way of
disambiguating commands and data. If your program is one of these, then
it can provide completion for commands, data, or both.
The following sections describe how your program and Readline
cooperate to provide this service.

2.6.1 How Completing Works

In order to complete some text, the full list of possible completions
must be available. That is, it is not possible to accurately
expand a partial word without knowing all of the possible words
which make sense in that context. The Readline library provides
the user interface to completion, and two of the most common
completion functions: filename and username. For completing other types
of text, you must write your own completion function. This section
describes exactly what such functions must do, and provides an example.

There are three major functions used to perform completion:

The user-interface function rl_complete(). This function is
called with the same arguments as other bindable Readline functions:
count and invoking_key.
It isolates the word to be completed and calls
rl_completion_matches() to generate a list of possible completions.
It then either lists the possible completions, inserts the possible
completions, or actually performs the
completion, depending on which behavior is desired.

The internal function rl_completion_matches() uses an
application-supplied generator function to generate the list of
possible matches, and then returns the array of these matches.
The caller should place the address of its generator function in
rl_completion_entry_function.

The generator function is called repeatedly from
rl_completion_matches(), returning a string each time. The
arguments to the generator function are text and state.
text is the partial word to be completed. state is zero the
first time the function is called, allowing the generator to perform
any necessary initialization, and a positive non-zero integer for
each subsequent call. The generator function returns
(char *)NULL to inform rl_completion_matches() that there are
no more possibilities left. Usually the generator function computes the
list of possible completions when state is zero, and returns them
one at a time on subsequent calls. Each string the generator function
returns as a match must be allocated with malloc(); Readline
frees the strings when it has finished with them.
Such a generator function is referred to as an
application-specific completion function.

Function: int rl_complete(int ignore, int invoking_key)

Complete the word at or before point. You have supplied the function
that does the initial simple matching selection algorithm (see
rl_completion_matches()). The default is to do filename completion.

Variable: rl_compentry_func_t * rl_completion_entry_function

This is a pointer to the generator function for
rl_completion_matches().
If the value of rl_completion_entry_function is
NULL then the default filename generator
function, rl_filename_completion_function(), is used.
An application-specific completion function is a function whose
address is assigned to rl_completion_entry_function and whose
return values are used to generate possible completions.

2.6.2 Completion Functions

Here is the complete list of callable completion functions present in
Readline.

Function: int rl_complete_internal(int what_to_do)

Complete the word at or before point. what_to_do says what to do
with the completion. A value of `?' means list the possible
completions. `TAB' means do standard completion. `*' means
insert all of the possible completions. `!' means to display
all of the possible completions, if there is more than one, as well as
performing partial completion. `@' is similar to `!', but
possible completions are not listed if the possible completions share
a common prefix.

Function: int rl_complete(int ignore, int invoking_key)

Complete the word at or before point. You have supplied the function
that does the initial simple matching selection algorithm (see
rl_completion_matches() and rl_completion_entry_function).
The default is to do filename
completion. This calls rl_complete_internal() with an
argument depending on invoking_key.

Function: int rl_possible_completions(int count, int invoking_key)

List the possible completions. See description of rl_complete
(). This calls rl_complete_internal() with an argument of
`?'.

Function: int rl_insert_completions(int count, int invoking_key)

Insert the list of possible completions into the line, deleting the
partially-completed word. See description of rl_complete().
This calls rl_complete_internal() with an argument of `*'.

Function: int rl_completion_mode(rl_command_func_t *cfunc)

Returns the appropriate value to pass to rl_complete_internal()
depending on whether cfunc was called twice in succession and
the values of the show-all-if-ambiguous and
show-all-if-unmodified variables.
Application-specific completion functions may use this function to present
the same interface as rl_complete().

Returns an array of strings which is a list of completions for
text. If there are no completions, returns NULL.
The first entry in the returned array is the substitution for text.
The remaining entries are the possible completions. The array is
terminated with a NULL pointer.

entry_func is a function of two args, and returns a
char *. The first argument is text. The second is a
state argument; it is zero on the first call, and non-zero on subsequent
calls. entry_func returns a NULL pointer to the caller
when there are no more matches.

A generator function for filename completion in the general case.
text is a partial filename.
The Bash source is a useful reference for writing application-specific
completion functions (the Bash completion functions call this and other
Readline functions).

A completion generator for usernames. text contains a partial
username preceded by a random character (usually `~'). As with all
completion generators, state is zero on the first call and non-zero
for subsequent calls.

2.6.3 Completion Variables

A pointer to the generator function for rl_completion_matches().
NULL means to use rl_filename_completion_function(),
the default filename completer.

Variable: rl_completion_func_t * rl_attempted_completion_function

A pointer to an alternative function to create matches.
The function is called with text, start, and end.
start and end are indices in rl_line_buffer defining
the boundaries of text, which is a character string.
If this function exists and returns NULL, or if this variable is
set to NULL, then rl_complete() will call the value of
rl_completion_entry_function to generate matches, otherwise the
array of strings returned will be used.
If this function sets the rl_attempted_completion_over
variable to a non-zero value, Readline will not perform its default
completion even if this function returns no matches.

Variable: rl_quote_func_t * rl_filename_quoting_function

A pointer to a function that will quote a filename in an
application-specific fashion. This is called if filename completion is being
attempted and one of the characters in rl_filename_quote_characters
appears in a completed filename. The function is called with
text, match_type, and quote_pointer. The text
is the filename to be quoted. The match_type is either
SINGLE_MATCH, if there is only one completion match, or
MULT_MATCH. Some functions use this to decide whether or not to
insert a closing quote character. The quote_pointer is a pointer
to any opening quote character the user typed. Some functions choose
to reset this character.

Variable: rl_dequote_func_t * rl_filename_dequoting_function

A pointer to a function that will remove application-specific quoting
characters from a filename before completion is attempted, so those
characters do not interfere with matching the text against names in
the filesystem. It is called with text, the text of the word
to be dequoted, and quote_char, which is the quoting character
that delimits the filename (usually `'' or `"'). If
quote_char is zero, the filename was not in an embedded string.

Variable: rl_linebuf_func_t * rl_char_is_quoted_p

A pointer to a function to call that determines whether or not a specific
character in the line buffer is quoted, according to whatever quoting
mechanism the program calling Readline uses. The function is called with
two arguments: text, the text of the line, and index, the
index of the character in the line. It is used to decide whether a
character found in rl_completer_word_break_characters should be
used to break words for the completer.

Variable: rl_compignore_func_t * rl_ignore_some_completions_function

This function, if defined, is called by the completer when real filename
completion is done, after all the matching names have been generated.
It is passed a NULL terminated array of matches.
The first element (matches[0]) is the
maximal substring common to all matches. This function can
re-arrange the list of matches as required, but each element deleted
from the array must be freed.

Variable: rl_icppfunc_t * rl_directory_completion_hook

This function, if defined, is allowed to modify the directory portion
of filenames Readline completes.
It could be used to expand symbolic links or shell variables in pathnames.
It is called with the address of a string (the current directory name) as an
argument, and may modify that string.
If the string is replaced with a new string, the old value should be freed.
Any modified directory name should have a trailing slash.
The modified value will be used as part of the completion, replacing
the directory portion of the pathname the user typed.
At the least, even if no other expansion is performed, this function should
remove any quote characters from the directory name, because its result will
be passed directly to opendir().

The directory completion hook returns an integer that should be non-zero if
the function modifies its directory argument.
The function should not modify the directory argument if it returns 0.

Variable: rl_icppfunc_t * rl_directory_rewrite_hook;

If non-zero, this is the address of a function to call when completing
a directory name. This function takes the address of the directory name
to be modified as an argument. Unlike rl_directory_completion_hook,
it only modifies the directory name used in opendir, not what is
displayed when the possible completions are printed or inserted. It is
called before rl_directory_completion_hook.
At the least, even if no other expansion is performed, this function should
remove any quote characters from the directory name, because its result will
be passed directly to opendir().

The directory rewrite hook returns an integer that should be non-zero if
the function modfies its directory argument.
The function should not modify the directory argument if it returns 0.

Variable: rl_icppfunc_t * rl_filename_stat_hook

If non-zero, this is the address of a function for the completer to
call before deciding which character to append to a completed name.
This function modifies its filename name argument, and the modified value
is passed to stat() to determine the file's type and characteristics.
This function does not need to remove quote characters from the filename.

The stat hook returns an integer that should be non-zero if
the function modfies its directory argument.
The function should not modify the directory argument if it returns 0.

Variable: rl_dequote_func_t * rl_filename_rewrite_hook

If non-zero, this is the address of a function called when reading
directory entries from the filesystem for completion and comparing
them to the partial word to be completed. The function should
perform any necessary application or system-specific conversion on
the filename, such as converting between character sets or converting
from a filesystem format to a character input format.
The function takes two arguments: fname, the filename to be converted,
and fnlen, its length in bytes.
It must either return its first argument (if no conversion takes place)
or the converted filename in newly-allocated memory. The converted
form is used to compare against the word to be completed, and, if it
matches, is added to the list of matches. Readline will free the
allocated string.

Variable: rl_compdisp_func_t * rl_completion_display_matches_hook

If non-zero, then this is the address of a function to call when
completing a word would normally display the list of possible matches.
This function is called in lieu of Readline displaying the list.
It takes three arguments:
(char **matches, intnum_matches, intmax_length)
where matches is the array of matching strings,
num_matches is the number of strings in that array, and
max_length is the length of the longest string in that array.
Readline provides a convenience function, rl_display_match_list,
that takes care of doing the display to Readline's output stream. That
function may be called from this hook.

Variable: const char * rl_basic_word_break_characters

The basic list of characters that signal a break between words for the
completer routine. The default value of this variable is the characters
which break words for completion in Bash:
" \t\n\"\\'`@$><=;|&{(".

Variable: const char * rl_basic_quote_characters

A list of quote characters which can cause a word break.

Variable: const char * rl_completer_word_break_characters

The list of characters that signal a break between words for
rl_complete_internal(). The default list is the value of
rl_basic_word_break_characters.

Variable: rl_cpvfunc_t * rl_completion_word_break_hook

If non-zero, this is the address of a function to call when Readline is
deciding where to separate words for word completion. It should return
a character string like rl_completer_word_break_characters to be
used to perform the current completion. The function may choose to set
rl_completer_word_break_characters itself. If the function
returns NULL, rl_completer_word_break_characters is used.

Variable: const char * rl_completer_quote_characters

A list of characters which can be used to quote a substring of the line.
Completion occurs on the entire substring, and within the substring
rl_completer_word_break_characters are treated as any other character,
unless they also appear within this list.

Variable: const char * rl_filename_quote_characters

A list of characters that cause a filename to be quoted by the completer
when they appear in a completed filename. The default is the null string.

Variable: const char * rl_special_prefixes

The list of characters that are word break characters, but should be
left in text when it is passed to the completion function.
Programs can use this to help determine what kind of completing to do.
For instance, Bash sets this variable to "$@" so that it can complete
shell variables and hostnames.

Variable: int rl_completion_query_items

Up to this many items will be displayed in response to a
possible-completions call. After that, readline asks the user if she is sure
she wants to see them all. The default value is 100. A negative value
indicates that Readline should never ask the user.

Variable: int rl_completion_append_character

When a single completion alternative matches at the end of the command
line, this character is appended to the inserted completion text. The
default is a space character (` '). Setting this to the null
character (`\0') prevents anything being appended automatically.
This can be changed in application-specific completion functions to
provide the "most sensible word separator character" according to
an application-specific command line syntax specification.

Variable: int rl_completion_suppress_append

If non-zero, rl_completion_append_character is not appended to
matches at the end of the command line, as described above.
It is set to 0 before any application-specific completion function
is called, and may only be changed within such a function.

Variable: int rl_completion_quote_character

When Readline is completing quoted text, as delimited by one of the
characters in rl_completer_quote_characters, it sets this variable
to the quoting character found.
This is set before any application-specific completion function is called.

Variable: int rl_completion_suppress_quote

If non-zero, Readline does not append a matching quote character when
performing completion on a quoted string.
It is set to 0 before any application-specific completion function
is called, and may only be changed within such a function.

Variable: int rl_completion_found_quote

When Readline is completing quoted text, it sets this variable
to a non-zero value if the word being completed contains or is delimited
by any quoting characters, including backslashes.
This is set before any application-specific completion function is called.

Variable: int rl_completion_mark_symlink_dirs

If non-zero, a slash will be appended to completed filenames that are
symbolic links to directory names, subject to the value of the
user-settable mark-directories variable.
This variable exists so that application-specific completion functions
can override the user's global preference (set via the
mark-symlinked-directories Readline variable) if appropriate.
This variable is set to the user's preference before any
application-specific completion function is called, so unless that
function modifies the value, the user's preferences are honored.

Variable: int rl_ignore_completion_duplicates

If non-zero, then duplicates in the matches are removed.
The default is 1.

Variable: int rl_filename_completion_desired

Non-zero means that the results of the matches are to be treated as
filenames. This is always zero when completion is attempted,
and can only be changed
within an application-specific completion function. If it is set to a
non-zero value by such a function, directory names have a slash appended
and Readline attempts to quote completed filenames if they contain any
characters in rl_filename_quote_characters and
rl_filename_quoting_desired is set to a non-zero value.

Variable: int rl_filename_quoting_desired

Non-zero means that the results of the matches are to be quoted using
double quotes (or an application-specific quoting mechanism) if the
completed filename contains any characters in
rl_filename_quote_chars. This is always non-zero
when completion is attempted, and can only be changed within an
application-specific completion function.
The quoting is effected via a call to the function pointed to
by rl_filename_quoting_function.

Variable: int rl_attempted_completion_over

If an application-specific completion function assigned to
rl_attempted_completion_function sets this variable to a non-zero
value, Readline will not perform its default filename completion even
if the application's completion function returns no matches.
It should be set only by an application's completion function.

Variable: int rl_sort_completion_matches

If an application sets this variable to 0, Readline will not sort the
list of completions (which implies that it cannot remove any duplicate
completions). The default value is 1, which means that Readline will
sort the completions and, depending on the value of
rl_ignore_completion_duplicates, will attempt to remove duplicate
matches.

Variable: int rl_completion_type

Set to a character describing the type of completion Readline is currently
attempting; see the description of rl_complete_internal()
(see section 2.6.2 Completion Functions) for the list of characters.
This is set to the appropriate value before any application-specific
completion function is called, allowing such functions to present
the same interface as rl_complete().

Variable: int rl_completion_invoking_key

Set to the final character in the key sequence that invoked one of the
completion functions that call rl_complete_internal(). This is
set to the appropriate value before any application-specific completion
function is called.

Variable: int rl_inhibit_completion

If this variable is non-zero, completion is inhibited. The completion
character will be inserted as any other bound to self-insert.

2.6.4 A Short Completion Example

Here is a small application demonstrating the use of the GNU Readline
library. It is called fileman, and the source code resides in
`examples/fileman.c'. This sample application provides
completion of command names, line editing features, and access to the
history list.

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